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/sci/ - Science & Math

 Name Options Subject Comment Verification 4chan Pass users can bypass this verification. [Learn More] [Login] File Please read the Rules and FAQ before posting.Use TeX with tags for inline and [eqn] tags for block equations.Right-click equations to view the source.  05/04/17 New trial board added: /bant/ - International/Random 10/04/16 New board for 4chan Pass users: /vip/ - Very Important Posts 06/20/16 New 4chan Banner Contest with a chance to win a 4chan Pass! See the contest page for details. [Hide] [Show All] The 4chan Vtuber Competition is over. Click here to see the winning entry! [Catalog] [Archive] You all know this is what boston dynamics is really aiming to achieve right or at least this is what the pentagon will be paying billions towards BD to create. How long do you think before we get there, 20 to 40 years? 82 replies and 11 images omitted. Click here to view. >> >>10089152 >Same as an American without a snickers bar and a mountain dew. That's what the backpack is for. >> >>10086144 So you're saying that you want it hunting down babies in camo That's an idea I'd gofundme >> >>10085665 Who made this shitty graph, it's two separate incompatible graphs on top of each other that confused the hell out of me >What kinda battery you want bro? Power. >No I mean like how long do you want to fly for? 230 Watts >> >>10089179 >i'm a kid and never saw a secondary axis before >> >>10080590 Imagine all of the jobless people there would be if robots replaced law enforcement or military roles. Hey /sci/. Im a math and EE undergrad thats currently teaching math to a class of 17-18yos highschool seniors that come from a very poor environment. I need some guidance. I teach one, 3 hour long class a week. I make a latex transcript of every class and upload it to a shared drive folder they all have access to. I also gave them a homework for preparation for the first exam and told them that the exercises in the homework are exactly the ones theyre gonna find in the exam. I take all the time in the world to make sure they understand, I stop the class to explain away any question anyone may have. So much It took me 3 weeks to teach what I wanted to teach in 1 class. I even gave them my number so that they could add me to a group chat so that they could ask any questions throughout the week. But man this is all in vain. They only complain about not understanding anything, I ask them what is it they dont understand and they dont even know! Only one kid asked about a problem in the homework today (the night before the exam) and it was about literally the first one in the whole goddamn thing! Comment too long. Click here to view the full text. 82 replies and 6 images omitted. Click here to view. >> >>10089202 you don't understand. you think that that is "interesting", it is exactly the opposite of that. They're not going to think "huh, that's weird". Only a special kind of hard-core autist or nerd who cares passionately about patterns in arbitrary things, will think that. Because you are that nerd you can't empathise with the kind of hostility that your approach evokes in the other type of people (everyone else) >> >>10086675 Oh man, you didnt even put a 4x4 system of equations so they can solve using the echeleon form, you probably call this method fuerma escadita if my spanish is not that rusted. The secret is: you need to ask for more of the students, this level of content is too shallow and they'll perform poorly because they dont feel challwnged enough >> >>10087528 i learned french thank you very much >> >>10089219 I can definitely see how I'd have trouble relating to those with no real interest for these topics. What sort of things would you recommend showing to a general audience to spark at least some interest in advanced math? Or maybe demonstrations are not the right way to approach this? >> >>10086675 I strongly recommend you watch the movie stand and deliver, just passing information isnt enough, you have to make emotional understanding File: 1520983214668.jpg (16 KB, 385x382) 16 KB JPG >prof starts telling a joke 203 replies and 63 images omitted. Click here to view. >> >prof tells class the US response to 9/11 "didn't fly" with the international community >> >>10089018 Don't forget south americans, we are pretty smart. >> >genetics prof is a 30s qt from brazil >new this semester >tries to be nice but nobody gives a fuck >the lab is always closed and we have to wait with her until the head-prof fucking open it >she is visible sad and tired Fuck >> File: 1488485908488~01.jpg (34 KB, 375x375) 34 KB JPG >>10089262 >> >>10089262 >>10089296 [Urge to give her a good time intensifies] Does a fusion reactor get us a single stage to orbit fusion rocket? 2 replies omitted. Click here to view. >> >>10089201 >The benefit of this is the velocity in which the the products of the reaction are shoved out, which is better than chemical rockets. I'm sure you have some basis to believe this rather than pulling it out of your asshole. >> >>10089272 >https://en.wikipedia.org/wiki/Fusion_rocket Christ you are a retarded conflict seeking monkey. If you actually cared about determining how a fusion drive would work you would just look it up yourself. >> https://www.amazon.co.jp/%E3%82%B0%E3%83%AD%E3%83%83%E3%82%B7%E3%83%BC-GLOSSY-%E3%83%AF%E3%83%BC%E3%82%AF%E3%82%B7%E3%83%A5%E3%83%BC%E3%82%BA-%E3%82%B0%E3%83%AD%E3%83%83%E3%82%B7%E3%83%BCGY-100-6A661/dp/B01HHUV4LY/ref=sr_1_152?s=shoes&ie=UTF8&qid=1540272441&sr=1-152&refinements=p_n_feature_six_browse-bin%3A2189414051 >> >>10089285 >this thing that doesn't exist and we have no idea how to make is better than chemical propulsion Great. >> If we have fusion (and therefore virtually unlimited energy to produce almost anything our hearts desire) can we produce star-faring spacecraft? 41 replies and 5 images omitted. Click here to view. >> >>10085273 barad-dur childrens' hospital >> >>10085273 I've seen way worsts... I don't know what is it with surgeons that they love this dungeon-like style for their operating rooms... I mean, I know these guys love to keep it classic but come on! >> >>10081393 Looks like a scallop. yumm >> >>10081393 Amazing how somebody could literally fuck up your entire physical and mental perception of the world with a twitch of their finger >> >>10082362 Nobody likes doctors fuck you File: sound.png (242 KB, 1100x739) 242 KB PNG I have a question about sound /sci/. Say you're sitting in a room, hearing someone talking while a fly buzzes around you and an ambulances passes nearby with its sirens on. Now, the tiny increases and decreases of pressure (the sound wave) that reaches your ears is a superposition of all the individual sound waves, correct? We know we can decompose this superposition of waves back into its individual source waves with Fourier series. Now, here's my question, every source I've read about how the ear distinguishes frequencies basically says that the inner ear has different parts that are sensitive to different frequencies, I'm not interested in the specifics right now. My question is this, the pressure wave that reaches the inner ear is a superposition of several source waves, with a frequency that is different from the source waves. Decomposing the wave into its fundamental frequencies is a mathematical abstraction is it not? Physically speaking, how can any instrument be sensitive to a specific frequency in a sound wave that is of a different frequency? 20 replies and 2 images omitted. Click here to view. >> >>10089168 Literally this. It's a simple sum of all the parts. If two waves arrive in your ear at the same time they either cause the complete waveform to grow or fakl in amplitude depending on the phase relationship of the waves. If the wave functions are identical, the two extremes are either that the amplitude is doubled or that it is nulled. Keep in mind that the difference of waves in general is so fast that you have to calculate about 20 peaks per second at a minimum, and over 20000 at maximum. The fluctuations affect each other visually in the waveform, but don't really interact. What this mean for example is that if you have a complete song and it's instrumental version, you can separate the vocals by aligning the waveforms carefully and flipping the phase of the instrumental. If the volume is matched properly only the vocals should remain (and most likely some high-end artefacts due to the mastering process.). >> >>10089193 Oh, and you need at least the 20 or 20000 peaks arriving in your ear at a near constant rate for you to recognize the tone. If it fluctuates too much it becomes noise. >> >>10089193 >>10089199 OP already understood superposition, you're just digressing into some confusing extraneous notions here >> >>10085987 OP. Let's talk physics. Mechanical waves are traveling forms of energy where the local pressure variations and particle displacements. These two waves are in quadrature for lossless media (idealized cases) and interact with matter at an atomic level. Mechanical structures can be conceptualized as mass-springs systems and the most important distinction being that the spring constant (if we're using a Hooke's law approach) is effectively different for different media. Going from a rarefied substance (like air) to a solid (ear hair or what-have-you) is kind of like having a ping pong ball attached to a rubber band trying to cause different pendulums to swing in a set arc length [for poops and giggles, +5/-5 °, but the number doesn't matter for the illustration]. In order to get this small angle oscillation with your rubber-band ping pong ball contraption, you would have no luck getting a +/-5° swing from say a wrecking ball at the end of 500' steel braid cord... except if you could use 1000s of ping pong balls and you some how rigged up your much more massive set of conjointly moving balls to move much, much slower. It'd be tough, right, but there's a limit as you approach the absurd infinity that you can see that yes, with enough slowly moving ping pong balls tapping over a long period of time one could get the bastard swaying. Conversely, if you task was to move +/-5° say another ping pong ball attached to a 10' string, we'll you could probably do so with a single ping pong ball and would be able to oscillate it back and forth much quicker by using shorter, quicker pulses to tap this pendulum than what you could with the wrecking ball example. This example is just trying to connect everyday observations and scenarios that you know exist with applications is real life. Pendulums with small angle displacements are simple harmonic oscillators and have a very well defined harmonic frequency that they operate. >> >>10089227 (continued) In the wrecking ball excitation, the natural resonance of the small angle excitation only occurred when we used longer time periods between tapping the big fucker with our ping pong balls, as a result this massive system would have a (1/period) low natural frequency. If we were to use the same excitation frequency on the wrecking ball as we did the 10' ping pong ball, the wrecking ball would be piss poor at achieving the +/-5° we were trying to hit and may never actually hit it (same failure would be seen of trying low frequency excitation with the ping-pong ball pendulum - the ping pong ball would settle much more quickly before the next excitation pulse had a change to add energy to the system). Thus, when excitation frequencies that are not near the resonance frequency of the object we are trying to excite, they are largely fucking ignored. In this way, the object's natural resonance (based on the mass-spring system of the interacting objects) acts effectively as a very narrow bandpass filter - letting only frequencies near it's natural frequency actually have any observable impact on it's response (pendulum displacement in this scenario). Likewise, long hairs don't give a fuck about 20 kHz and short hairs don't give a fuck about 100 Hz poritons of the signals. Each hair acts like a filter about it's natural resonance (largely determined by the length/mass of the hair) and will selectively respond to very narrow ranges of frequencies. Note: This isn't a binary example. If your natural frequency is 100 Hz and you hit it with 90 Hz, you'll still get some signal but lower than if it was a 90 Hz hair. But your brain already prepared to interpret these findings... Any psychiatrists on /sci/? Do you actually help people or just give out happy pills? 3 replies omitted. Click here to view. >> Protip. Psychs are human beings. This means some things. Firstly not all of them are equal. Secondly they are greatly flawed by inherant human greed and self interest. What this means for you is that the vast majority of them will only make a token effort at actually helping you. Not just out of disinterest but also because of their own dull minds. You are their paycheck. Now I will let you know they are also very dangerous because of their self interest. They will drug you and give you advice just to run experiments for their own learning process. It can get worse. You could be drugged and abused. They could brainwash you to accept the mistreatment as usual. You will lose all power and control over your own life. Now because you are weak the people around you will begin to disrespect and even ignore you. Before long the people closest to you will start to see they can use you for their own self interest as well. They will justify their behaviour because you qill have changed. Because of the drugs and the changes to your personality you will just passively accept all the insanity around you. Be careful. >> >>10089203 >What this means for you is that the vast majority of them will only make a token effort at actually helping you. Not just out of disinterest but also because of their own dull minds. You are their paycheck. Psychiatrists have one of the highest suicide rates. Dealing with people’s traumas all day long is horrible work. Don’t be a cunt. >> >>10089206 The less psychologists the better. Honestly I have yet to see a single example of a psychologist who has had a positive influence in anyones life. I have seen a handful of examples of them totally screwing other people for their own self interest. I myself have suffered as a result of their toxic influence. Show me a good one. Show me results. Psychologists are parasites who feed upon the weak. >> >>10089161 You're honestly better off seeking a priest or religious person. >> >>10089206 Yes, prescribing people pills that will make them dumb enough to not have problems anymore is a job I would commit suicide at too. File: chris-langan.jpg (11 KB, 464x272) 11 KB JPG >A-anon, ha-have you read my CTMU yet ? >I believe its at least as important as einsteins theory. >You know why I have a big head anon, It correlates with intelligence. >I believe the world should be ruled by an elitist oligopole of high IQ people only, with me being the overlord. I am the smartest man alive. >Yes anon I dropped out of college to work as a bouncer. I was just too smart for the people there. >You know, I had the best Idea about conciousness it was really cool, but then I got in a bar fight because im real tough and then I forgot it. But it was really cool and it explained everything ! 102 replies and 21 images omitted. Click here to view. >> >>10086466 That's not true unless your "either" is an exclusive-or, which I assume is what you meant—i.e. that where [math]T and $P$ are collections of sentences, everything is a model of $T$ or of $P$ but that $T \cup P$ is inconsistent.

The following is true: if $T$ and $P$ are collections of sentences in some first-order language $\mathcal{L}$ such that every structure over $\mathcal{L}$ is a model of $T$ or $P$ but that $T \cup P$ is inconsistent, then there is a finite $D \subset T$ such that the set of models of $D$ is the set of models of $T$ (and by symmetry likewise for $P$). So any definable partition of the set of all structures into two pieces is "finitely definable".

Here is a proof which, naturally, does use compactness. Suppose for contradiction that for every finite $D \subset T$, there were some model $\mathfrak{A}$ of $D$ that is not a model of $T$. Then, by exclusivity of our "either", $\mathfrak{A}$ is a model of $P$. Thus $P \cup D$ is consistent. But then $P \cup D$ is consistent for all finite $D \subset T$, so by compactness, because $P \cup T$ is finitely consistent, $P \cup T$ is consistent. Contradiction.
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>>10086222
Anon, you don't understand. That's exactly the issue. That it's unironically correct.
>>
If Helene is evil then there is a high likelihood of Laura, a/k/a Langan, also being evil.
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>>10086538
That makes sense, that's exactly what I was asking. thank you!
>>
Any other based caps from him?

Or is this just Greenpeace bullshit?
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>>10085633
Probably and the truth of the matter is on a large scale we're never going to get around to fixing it the only viable option is prepare for the eventual shift and endure
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>>10085890
cringe
>>
1 minute summary for idiots.

1. The climate is changing. It's a fact. Everyone who is qualified to actually know what they are talking about agrees to that. It's scientific consensus.

2. We are past the point of no return, it can't be stopped, but it could be considerably mitigated with immediate action.

3. Climate change will not wipe out humanity even in the worse case scenario. We're not all going to die. People who say that are scaremongering.

4. No matter what, it is going to suck. There will be serious consequences (worse storms, disease spreading, drought, sea level rise, etc.). It's going to be a big, expensive mess, and it is both easier and cheaper to start working on it now, compared to working on it latter.

5. Anyone who tells you something otherwise is either pushing an agenda or doesn't know what they are talking about.
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>>10085633
Let's say we humans 100% stop all our pollution tomorrow.

Now what?
How are you going to stop all the natural methane that comes from the ground every year and the ASS LOAD of C02 and other horrid shit that comes from Volcanoes every year? What about the natural global cooling and warming that's always happened for billions of years on Earth that's 1000% beyond our ability to control?

What we produce as human is insignificant to what the Earth naturally produces and always has for billions of years and is massively arrogant to think man has even the slightest effect on a fucking planets climate. Greenpeace is a bunch of hippy armchair "scientist" that enjoy hearing themselves talk high and mighty like their shit dont stink.

Greenpeace would have everyone move to the Moon or Mars and watch Earth then be like "Well shit its still happening even though we are gone for thousands of years now....sorry guys"
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>>10089143
>pushing an agenda
sure does sound like thats what your doing there Greenpeace

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is it possible to produce certain psychotropic drugs yourself for recreational use? How much money would I have to invest in a lab?
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>>10088757
>>10088768
Albeit last I checked was a couple years ago, /qa/ is literally r*eddit. Don’t go there
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>>10088505
why sell drugs when it can get you in jail. Sell fatty foods, its more addictive and perfectly legal, you can even sell it to kids
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>>10089077
>why sell drugs
Read, anon. Where the fuck do you think you are?

>for recreational use
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>>10088505
find certain toad, lick it like the hippies did, Enjoy free DMT
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>>10089197
Idiotic idea. Psilocybin-containing mushrooms are far more ubiquitous and safe.

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Freshman doing lab planning. I'm supposed to calculate the height of a building using:
-Metre ruler
-Protractor
-String
-Straw
-Blu Tack
-Sellotape
-Tape measure
-Pupillary distance ruler

Some of these items are red herrings and won't be actually used. Anyways, is there a way to calculate this without the classic shadow method? The sun is very tilted so I'm doubtful I'll get a good measure of the angle, and I'll probably measure the shadow length wrong too (may misjudge the base point).
In addition, I think there isn't going to be a shadow at all due to where we are doing the experiment. Sun will be behind us and I'm not sure if going behind the building is allowed.

Any thoughts?
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>>10089118
Thank you anon.
One unrelated thing question- is it possible to measure time in seconds using a bob-attached spring WITHOUT knowing mass of the bob or the spring's constant? Obvious answer to me is no, but they don't say they'll give those numbers so I'm in slight doubt here.

Regardless whether you answer the follow-up or not, thanks.
>>
similar triangles
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>>10089132
no, its not possible unless you first measure the period with an exact time as a reference - eg how many times it moves in 10 seconds

For pendulums you can get its period by putting the length of its string into the respective string-length-to-period formula
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>>10089148
Thanks anon, you've been of great help. I'll delete this post soon since it's no longer of use to anyone.
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>>10089090
this isnt the place for homework questions

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Do you think Lockheed Martin has made any secretive advancements in fusion?
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>>10088353
No, that's meme marketing for government contract money
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>>10088563
Raytheon makes missiles not fusion.
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>>10088353
>Lockheed Martin
Remember them supporting Eestor?

Pepperidge farm remembers...
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>>10088353
It was probably free energy from lasers that they decoyed with fusion
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>>10088353
no b/c they are to busy making planes that dont fly. Big Gov would rather let some student 50k in debt do it for them for free.

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>Is X a meme major?
Unless it is Biomedical, Mechatronics, or Systems Engineering your major XE major is not a “meme”. Additional meme majors include chemical and nuclear engineers. They are challenging degrees but there are just not enough jobs to keep up with graduating students. Many bitter anons in these threads are ChemE students or unemployed ChemE graduates.

>Why is Mechatronics or Bio Engineering a meme degree?
They are often very shallow degrees at the undergraduate level. Students end up becoming a master of none and are outclassed by the more common disciplines. For the longest period of time these courses were only Master/PHD opportunities. A good undergraduate program is very rare for either discipline. Your meme state school isn’t one of those programs.

>I can’t find a job
What is your GPA? What is your experience? Is your resume shit? Do you interview well? When did you start looking?
>GPA
A GPA of 3.0 is the bare minimum for most companies.
>Experience
Experience is helpful but is not needed to get a job. You will have a much tougher time though and will need to grind out applications. College clubs and personal projects are good ways to get at least some experience if it is not professional experience.
>Resume
Post your resume if you want it to be reviewed. Try and quantify actions at your job, don’t just list your responsibilities. If you have no professional experience emphasize your school projects/clubs/personal projects.
>Interviewing
It helps to practice and write down your answers to question that you think you will be asked. Using Glassdoors can be helpful when trying to figure out what kind of questions specific companies ask.
>Candidate
You don’t need to be a 3.9 GPA, 3 internship, non white student to get a job in Engineering. Just keep in mind Apple/Boeing/Broadcom/Google/Intel/etc, don’t generally hire <3.0 GPA no experience autists that are incapable of talking to other human beings.

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>>10089026
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>>10088951
Can't you get a loan?
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>>10088951
live in a van.
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>fall for engineering meme
>realize want to do math instead
>will be in excess of hours if do
Fuck being an indecisive fuck
The jealousy I have for my math and physics buddies is real, Ive compared our courses and I get fuck all
On the bright side, we have great connects and I know Ill have a job as soon as I graduate, but the feels are real
>>
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Serious career/life question

I graduated with a Math/CS degree five years ago but I've been underemployed (and now unemployed) since then. Never got a development job. I'm smart and excellent at math though, my average was 87% (my school doesn't do GPA) which is nearly 4.0. I spent all my time studying, but never did any of the things you are actually supposed to do like network, apply for internships (and get laid) because of extreme social anxiety.

I'm 28 and thinking that I might be best off just starting over, with a new degree. Fuck competing with pajeets over some dumb code monkey job. I want something where I get to use mathematics or physics on the job, not writing code that any brainlet can do.

So I'm thinking that I'll go get a Bachelors in Electrical Engineering, reset the clock (hopefully). This time I'll do co-op, network properly, make friends, actually apply for internships and get to know my profs. Join clubs and shit. Maybe get involved with robotics, shit like that. Be a student instead of a nameless faceless number who just turned in assignments and wrote exams.

What do you guys think? Will I be able to make it? Could this actually work? Am I just going to be some weird freak or outcast? Will already having a Bachelors fuck me over in some way? Will having an employment gap fuck me?

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Does your university use smell tests?
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>>10088355
He sent this to the whole class
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>>10087898
>He doesn't ask his professor if he can use the office shower before getting help
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>>10087898
The legality of a smell test seems dubious at best in a quasi-government institution.
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>>10087898
>literally, LITERALLY penis inspections in colleges now
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>>10087898
beeeeeeeerrrrrrap......here you go teach.

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I failed my Transform Theory module. It's going to take me like 5 years to finish this 3 year degree. Hold me bros...
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>supposed to finish my master's degree last semester
>the programme requires a thesis
>took me 6 months to even dare asking a professor to be my director of thesis
>now have weekly meetings with him
>stay in bed playing games 6 days a week
>use the 7th day looking for random stupid questions to ask him to pretend I've been working
I hate myself
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>>10087836
Almost sounds like you're not going to get your master's at this rate.
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>>10087836
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>>10087856
Mathematics, and the thesis is related to ODE and Numerical Analysis, both very simple fields. I shouldn't have any excuse
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>>10087836
jesus i feel you

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